The present invention relates generally to an umbrella, and more particularly, to an umbrella which uses spherical mechanisms for opening and closing.
The umbrella or parasol dates back to at least 1350 B.C. and was originally designed for protection against the sun rather than rain. Today, although there is no structural or operational difference between the two, the term "umbrella" is used to designate an apparatus which provides protection from rain and snow, while the term "parasol" is used to designate an apparatus which provides sun protection. Several design characteristics of the umbrella have not changed since its creation. The umbrella has always maintained a dome shape with a pole in the middle which operates as a handle and actuator. Also, through most of its history, the umbrella has utilized a plurality of equidistantly spaced, identical four-bar planar mechanisms operated simultaneously by a single slider on the central handle for opening and closing the umbrella. In recent decades, more complex six and eight-bar planar mechanisms have replaced the historic four-bar mechanisms, allowing for more compact folding, though still folding by activation of a single slider on the central handle.
In general, the umbrella's planar mechanisms have complex mechanical linkages including ribs which extend along a plurality of equidistantly spaced radii from the central pole to the rim of the umbrella dome in the form a "spider-web" to support the umbrella dome. The use of planar mechanisms for opening and closing the umbrella has several disadvantages. One disadvantage is that since maximum protection from the elements is clearly beneath the center of the umbrella dome and since this space is occupied by the central pole, the umbrella user must always stand to one side of this pole and therefore never receives optimal protection. Another disadvantage is that since the four-bar planar linkages or mechanisms are designed to be small and compact near the umbrella's apex in order to maximize the head room under the umbrella, there must be long extensions to the umbrella rim for supporting the umbrella dome. These long extensions are weak and flexible and often permit the umbrella dome to flip inside-out when a gust of wind comes from up underneath the umbrella. A further disadvantage is that the stitching between ends of the individual ribs and the cover often becomes undone since the edges of the umbrella are held in place at eight stress points corresponding to ends of the ribs of each four, six or eight-bar planar mechanism.